What started as a somewhat novel experiment -- the glass screen protector GLAS.t for iPhone 4/4S -- has since become an entire product lineup for Spigen SGP. The company now offers glass screen protectors for the iPhone 5 and iPad mini, with multiple variants for each device. Today, we're looking at some of the company's most recent versions, and more are likely to come in the future. For the iPhone 5, there's GLAS.tR Slim ($35), while the iPad mini gets GLAS ($58) and GLAS.t ($58). All three are essentially the same basis concept, with design tweaks represented by the letters and terms following their names.

Each version of GLAS begins with a sheet of crystal clear glass sized perfectly to fit the screen of its respective device. They all adhere to the display with a dry application process; you just clean the screen, peel the backing off the glass, align it with the device’s Home Button and/or FaceTime camera, then press down. To that end, each package comes with a packaged alcohol wipe, microfiber cleaning cloth, squeegee, and a sheet of six Home Button stickers. These are useful to restore full access to the now-recessed Home Button, which otherwise starts a little under the edge of the glass.

GLAS.tR Slim is the most advanced option Spigen SGP offers for the iPhone 5. It’s 0.4mm thick, with a hole at the top for the earpiece, and one at the bottom for the Home Button. Like all of the protectors, it allows you to touch through without hindering the sensitivity of the display, and doesn’t diminish the Retina quality of text or images. Despite the “slim” name, it’s actually the same thickness as the standard GLAS.t, but 28% thinner than the normal GLAS.tR, which is not reviewed here. The big difference with this version is the rounded edges—Z-axis tapers—whereas all the other models have straight edges. This makes the edges less vulnerable to chipping, which has been one of our primary concerns with the GLAS family. We think they feel better too, but they’re more visible.

For the iPad mini, GLAS.t is just what you’d expect: 0.4 mm of glass. This version only has one opening, for the Home Button. As is the case with all iPad screen protectors, it’s somewhat more difficult to apply because dust and other contaminants have more surface area to cling to, despite your initial cleaning efforts. However, it looks good once installed properly, and we were pleased to find that it works with Smart Covers. GLAS is the same idea, with a black or white painted bezel matching the iPad mini’s. It’s really just a color variant, although we found that choosing contrasting colors, such as the black GLAS.t on a white iPad, looks pretty cool.

The GLAS family makes more sense for iPhones than iPads. Generally, your phone is subjected to more use and circumstances where the screen could be damaged than your tablet. The sheets of glass are also about half the price. We can wrap our heads around $30 or so for a glass protector in a world of $15 high-quality plastic alternatives, but close to $60 strikes us as far too much to pay for a mere screen cover. As we noted in our original GLAS.t review, once the GLAS breaks, it can’t really be reused and needs to be replaced. GLAS.tR Slim is improved, but also more expensive—the rounded edges constitute an important update that reduces the chances of damage. As such, it earns a strong general recommendation and a B+ rating. The iPad mini versions of GLAS and GLAS.t, on the other hand, simply cost too much to be truly practical options. Like their full-sized counterpart, they earn a limited recommendation.

Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
This iLounge article provides more information on this practice, known as revving.